Dredged Sludge Research Articles

Thermal study of an aged dredged sludge

A dredged sludge was studied to investigate the influence of ageing and of pretreatment on its drying rate, water sorption/retention, thermal mass loss, XRD and microstructure (SEM). Ageing caused change in particle thickness and specific surface, a gradual aggregation to form units of the size 10–50 μm, formation of macropores of similar size, unhomogeneity and fissures between aggregates and “super-aggregates”. Macropores were detectable by the initial drying rate especially at 45°C. They indicated a tendency of collapsing at a lower drying rate at 30°C. This is consistent with SEM observations. With ageing the aggregates were more compact and less sensitive to drying. The aggregated system indicated a higher initial drying rate (higher permeability), whereas stirring induced a lower drying rate, favouring the formation of compact laminar structure. XRD peak intensity was lowered with ageing due to decrease in crystallinity (stacking faults and/or decrease in crystallite size). The content of amorphous material was lowered as well, reducing water sorption/desorption, which indicated that the specific surface is lower. From the suitable microstructure induced by ageing some new phases may form (feldspar, zeolites), preferably in the coarser fraction of the sludge. This is disturbed by stirring which operation expels also carbonates from the particle edges and this may reduce the structural strength of the sludge. In aged bentonite suspension a similar tendency was observed of formation of specific microstructures capable of phase transformation, e.g. to feldspar.

Contribution of Stainless-Steel Slag to the Development of Strength for Seabed Hedoro

The utilization of industrial wastes as cement replacement material is one of the most desirable methods to solve environmental problems posed by the production of these wastes. Concerning beneficial aspects, the potential uses create new construction materials. There are only a few studies that have been reported on the effective utilization of slag obtained from stainless-steel factory. The objective of this study is, therefore, to illustrate the potential use of a stainless- steel slag as a blended cement material, and to elucidate the contribution of blended slag cement to the development of strength for seabed dredged sludge (hedoro). The present study investigates hardening effects through the two important strength parameters, unconfined compressive strength ( q u strength) and California bearing ratio (CBR). Evaluation on reaction rate of tricalcium silicate ( C 3 S ) using X-ray diffraction analysis is proposed, and representative data are obtained. Based on the experimental results, the q u . strength of the hedoro stabilized with slag cement is higher than that of cement-stabilized hedoro in all respects. It is concluded that the slag powders added significantly accelerate the initial reaction rate of C 3 S, resulting in an increase in short-term and long-term strength. The development of strength in relation to the hydration mechanism of C 3 S is then discussed.

Use of contaminated dredged sludge as a substratum for forest growth - case study

Preliminary research was done to assess the suitability of dredged sludge as a growing medium. On an experimental sludge site, consolidated and aged during 3 years, physical, chemical and biological environmental parameters were analysed. Cuttings of poplar clones were used to evaluate growing response, in comparison with identical clones on the nursery site. This study, conducted in order to attempt the potentiality of afforestation, affirms its intention. Afforestation seems to be possible. As a consequence, relatively high amounts of heavy metals will be introduced into the forest ecosystem.